Method for coating an annular article



Nov. 15, 1955 c. A. NICHOLS 2,723,918

METHOD FOR COATING AN ANNULAR ARTICLE Filed Nov. '17, 1950 2 Sheets-Sheet 1 //v VENTOB Nov. 15, 1955 c, NICHOLS 2,723,918

METHOD FOR COATING AN ANNULAR ARTICLE Filed Nov. 1'7, 1950 2 Sheets-Sheet 2 /N VEN T012 M %//M% yf M J i l 7% {9H4 34 4 T OBNE Y5 facture of commutators.

United States Patent 2,723,918 Patented Nov. 15, 1955 METHOD FOR COATING AN ANNULAR ARTICLE Charles A. Nichols, Anderson, Iud., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application November 17, 1950, Serial No. 156,166

3 Claims. (Cl. 11'718) This invention relates to commutators for dynamoelectric machines and its object is to reduce the cost of manu- This is accomplished by elimination of separate V-ring insulators which hereto have been punched and formed from sheet insulating material. In the place of separately formed V-ring insulators, the present invention provides for coating the V-rings with insulation of such character as to withstand the pressure to which the V-rings are subjected when building the commutator. The V-rings are provided with a satisfactory insulating layer by coating them with a suitable thermosetting plastic, such as Bakelite varnish, and depositing upon the coating, while wet, evenly distributed particles of fine sand. The rings are heated to harden the varnish and thereby to obtain a permanent insulating layer of sand particles bonded by the hardened varnish.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a large scale longitudinal sectional view of a commutator embodying the present invention.

Fig. 2 is a side view of apparatus for applying the varnish to a V-ring.

Fig. 3 is a view in the direction of arrow 3 in Fig. 2.

Fig. 4 which is aview in the direction of arrow 4 of Figs. 2 and 3 shows also a plan view of the device for applying sand.

Fig. 5 is a view in the direction of arrow 5 of Fig. 4 and it shows a part of the workholder for supporting the V-ring below the sand applying device.

Fig. 6 is an enlarged sectional view on line 66 of Fig. 4.

Referring to Fig. l, a commutator embodying the invention comprises an annulus of commutator bars 10 having dove-tail tangs 11 alternating with insulating separators 12. This annulus is retained in assembly by a tubular rivet or core 13, the end portions of which are shaped to provide flanges 14 engaging V-rings 15. Each ring is provided with a non-conducting layer 16 which insulates the V-ring from the bars 10. The mechanical strength of the non-conducting layer is suflicient to resist the force applied to the end portions of the core 13 to form the flanges against the V-rings. The insulating layer 16 is, preferably, particles of fine sand embedded in and bonded by a suitable varnish which adheres to the v-ring.

Referring to Fig. 2, a base 20 supports a frame 21 which supports a vessel 22 which holds a quantity of varnish,

the level of which is indicated at 23. Frame 21 supports a shaft 24 which is driven by a pulley 25 through a belt 26 connected with a pulley 27 attached to a shaft 28 (Fig. 4), the latter being driven by an electric motor operated through a speed reducer. Shaft 24 supports a yoke 30 supporting a shaft 31 connected with shaft 24 by mesh ing gears 32 and 33 attached respectively to shafts 24 and 31 which drive varnish applying rolls 34 and 35, respectively. Roll 34 extends below the level 23 of the varnish in vessel 22 and picks up the varnish and passes it to the roll 35 which sweeps across a V-ring 15 as shown in Fig. 6. During the application on the varnish, the V-ring is rotated by an electric motor operating through a speed reducer in a housing 41 to drive a shaft 42 connected by a coupling 43 with a shaft 44. The shaft 44 carries a cup-shaped head 45 which holds the V-ring 15. The varnish which the roll 35 applies to the V-ring coats not only the surface 15a engaged by the roll but also the surface 15b (Fig. 6) because, during rotation of the V-ring 15, some of the varnish which is received on surface 15a creeps around the corner and along the surface 15b, whereby selected portions only of the ring are coated.

The speed reducer housing 41 is supported by a bracket 51, the base of which rests upon the plate 20 and is pivoted on a screw 52. A peg 53 passing through a hole in the bracket base and a hole 53a in the plate 20 locates the V-ring on the Workholder in alignment with the roll 35. After the V-ring 15 has received a suflicient coating of varnish, the peg 53 is lifted from the hole 53a in plate 20 and the bracket 51 is moved by a handle 54 attached thereto counterclockwise about the pivot screw 52 in order to place the V-ring 15 on the workholder in alignment with a sand applying device. When so aligned, the peg 53 will be aligned with a hole 53b in plate 20.

The sand applying device comprises a vessel 60 supported by a bracket 61 attached to plate 20. The line dry sand contained in vessel 60 will pass through a passage 62 when a valve 63 is opened by turning a wing-plate 64 from the position shown in full lines to the dot-dash position 64' shown in Fig. 5. While the V-ring 15 is rotating, fine sand particles descend as a stream, indicated at 65, upon the wet varnish applied to the surfaces 15a and 15b (Fig. 6) of ring 15. The varnish used is preferably a heavy Bakelite varnish so that a relatively thick layer of insulation is provided. The application of sand continues until the wet varnish has retained a substantial quantity of sand particles.

After the sand is applied to the wet varnish on the rotating V-ring, the motor 40 is stopped and the coated V-ring is removed by moving a collar upwardly along shaft 44 in order to cause pins 56 to push the coated V- ring from the holder 45. When collar 55 is released, a spring 57 returns the collar 55 to normal position so as to retract the pins 56 from the V-ring receiving recess of the holder 45.

Before moving the varnished V-ring from the varnish applicator to the sand applicator, it is not necessary to stop rotation of the rolls 34 and 35. The yoke 30 is moved clockwise (Fig. 2) about shaft 24 into the position 30', thus, moving roll 35 to 35' to free the V-ring.

After removal of the varnish and sand coated V-ring from the workholder, it is baked in order to harden the varnish and produce a permanent insulating layer comprising particles of sand bonded to each other and to the V-ring by a heat-hardened varnish, said layer having compressive strength sufiicient to resist the force applied through the core 13 to cause the dove-tailed tangs 11 to be gripped by the V-rings.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. In a method for selectively coating a ring having an outer surface and a truncated conical inner surface, the

steps comprising providing a transfer wheel having a ditaneously rotating the ring in a plane 90 from the plane of rotation of the wheel for causing every portion of said conical surface to be contacted by the wheel whereby the inner truncated conical surface and said outer surface of the ring is selectively coated with said material.

2. The method as claimed in claim 1 together with the added step of moving the ring from said transfer Wheel and applying finely divided material to the coated surface only of the ring.

3. The method as claimed in claim 1 together with the added step of depositing sand particles on the coated surfaces of the ring.

References Cited in the file of this patent UNITED STATES PATENTS 396,334 Gilson Jan. 15, 1889 4 Brenizer May 18, Baekeland Dec. 7, Bradley July 11, Sloan Sept. 28, Gerleman Nov. 29, Elder et al. Oct. 13, Barringer June 15, Pilkington Oct. 28, Kaegi May 16, Arnold Nov. 10, Hall Feb. 14, Baldwin July 11, Rand May 15, Moulton Dec. 9, Keller Sept. 12, 

1. IN A METHOD FOR SELECTIVELY COATING A RING HAVING AN OUTER SURFACE AND A TRUNCATED CONICAL INNER SURFACE, THE STEPS COMPRISING PROVIDING A TRANSFER WHEEL HAVING A DIAMETER SO THAT THE WHEEL WHEN IN POSITION WITH RESPECT TO THE RING IS TANGENT TO THE CONICAL INNER SURFACE ONLY AT OPPOSED INNER EDGES THEREOF, ROTATING THE WHEEL FOR PICKING UP A FLUID MATERIAL FROM A REMOTE SUPPLY, TRANSFERRING THE MATERIAL FROM THE WHEEL ONTO THE RING AND SIMULTANEOUSLY ROTATING THE RING IN A PLANE 90* FROM THE PLANE OF ROTATION OF THE WHEEL FOR CAUSING EVERY PORTION OF SAID CONICAL SURFACE TO BE CONTACTED BY THE WHEEL WHEREBY THE INNER TRUNCATED CONICAL SURFACE AND SAID OUTER SURFACE OF THE RING IS SELECTIVELY COATED WITH SAID MATERIAL. 